For safety at work reasons, a circuit breaker which has been manufactured in accordance with the ANSI Standard, must, for removal from the switchgear assembly for example for maintenance purposes, have an unloaded energy store (generally a spring store) for the switching mechanism. To achieve this, it is necessary for the storage spring of the switching mechanism to be automatically unloaded during the removal process (EP 0 048 042).
To do this, it is known for the storage spring of the switching mechanism to be unloaded by way of a switching process which unloads the spring store at a defined point in the movement (the so-called unloading position) as a function of the crank revolutions of the movement drive. This unloading is carried out by low-load switching.
During the movement of the circuit breaker from its operating position to the unloading position, and/or to the removal position, the switching-off catch is activated intrinsically by its design for safety reasons. This switching-off catch is provided in order to initiate a switching-off process for the low-voltage circuit breaker.
In consequence, at the unloading position during the movement, the activation of the switching-on catch, which is provided in order to initiate a switching-on process, leads to low-load switching when the spring is loaded. In this case, the spring store is unloaded (DE 101 53 108 C1 and DE 100 65 090 C1), without the main contacts of the low-voltage circuit breaker closing. The interaction of the switching mechanism, of the switching-on catch, of the switching-off catch and of the energy store is known, for example from DE 100 10 727 C2 and DE 101 20 783 C1.
The switching-off catch for initiating a switching-off process remains activated at least until the circuit breaker has been moved to the removal position and the crank is removed. However, the known circuit breakers according to the prior art have the disadvantage that the switching-on catch for initiating a switching-on process remains in an activated state even after the spring store has been unloaded. Thus, it is not possible to carry out a functional test on the circuit breaker even after removal, without resetting the store unloading by operating the movement drive once again. However, this is undesirable since it would contravene the principles of safety at work.